Projection image pickup device and projection image pickup method

A projection image pickup method for an apparatus that includes a controller, a pulsed-light emitter that emits light according to light emission control of the controller, an optical sensor that is exposed according to exposure control of the controller and generates an output signal indicating an amount of exposure, a reference timing generator that generates a signal indicating an operation reference timing, and a signal processor, the method comprising:

• performing exposure control over the optical sensor in synchronization with the operation reference timing, by the controller, during a first exposure period in a frame;
• causing the pulsed-light emitter to emit light in synchronization with the operation reference timing and performing exposure control over the optical sensor, by the controller, during a second exposure period in the frame;
• causing the pulsed-light emitter to emit light in synchronization with the operation reference timing and performing exposure control over the optical sensor in synchronization with a timing obtained by adding a predetermined delay time to the operation reference timing, by the controller, during a third exposure period in the frame;
• calculating a differential signal between an output signal from the optical sensor in the second exposure period and an output signal from the optical sensor in the first exposure period as a first differential signal, by the signal processor;
• calculating a differential signal between an output signal from the optical sensor in the third exposure period and the output signal from the optical sensor in the first exposure period as a second differential signal, by the signal processor;
• and
• calculating a sum total of at least two differential signals including the first differential signal and the second differential signal, by the signal processor.

A projection image pickup device, comprising:

• a pulsed-light emitter;
• an optical sensor;
• a reference timing generator that generates a signal indicating an operation reference timing;
• a controller;
• and
• a signal processor,
• wherein during a first exposure period in a frame, the controller performs exposure control over the optical sensor in synchronization with the operation reference timing,
• during a second exposure period in the frame, the controller causes the pulsed-light emitter to emit light in synchronization with the operation reference timing and performs exposure control over the optical sensor,
• during a third exposure period in the frame, the controller causes the pulsed-light emitter to emit light in synchronization with the operation reference timing and performs exposure control over the optical sensor in synchronization with a timing obtained by adding a predetermined delay time to the operation reference timing,
• the pulsed-light emitter emits light according to light emission control of the controller,
• the optical sensor is exposed according to the exposure control of the controller and outputs an output signal indicating an amount of exposure to the signal processor, and
• the signal processor
• calculates an average value of an output signal from the optical sensor in the second exposure period and an output signal from the optical sensor in the third exposure period, and
• outputs a differential signal between the average value and an output signal from the optical sensor in the first exposure period.